0x0b, 0x0c color temp increment and temp request (i have no idea how to use that, but default is good) 0x10 (black level), keep it on 50 0x12 contrast, keep it on 50 (probably)
0x6b brightness (backlight), default: 50, max 100
Gamma can't be configured, mine tablet has sRGB gamma (what I would expect from any sane graphics tool)
How-to use these?
Install ddccontrol
ddccontrol -r 0x6b -w 50 dev:/dev/i2c-1
// Assuming your tablet has i2c-1 and you want to set brightness to 50%
ddcutil setvcp 6b 50